Ergonomic ball chair



FIG. 1 is a top perspective view of an ergonomic ball chair showing my new design;

FIG. 2 is a bottom perspective view thereof;

FIG. 3 is a front elevated view thereof;

FIG. 4 is a rear elevated view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a right elevated view thereof; and,

FIG. 8 is a left elevated view thereof.

The broken lines showing of a wheel assembly in FIGS. 1-8, the broken lines showing of an arm rest assembly in FIGS. 1-8, and the broken lines showing of a rear support assembly in FIGS. 1-2, FIGS. 4-5, and FIGS. 7-8 are included for the purpose of showing environmental structure and form no part of the claimed design. 

CLAIM The ornamental design for an ergonomic ball chair, as shown and described. 